There are a certain number of plants or apparatuses which require a visual inspection (for example walls or contents, general wear, etc.); this cannot be effected directly, however, due to hostile or aggressive environmental conditions, or due to the exposure to hazards to which a human being can be subjected when gaining access to said hostile environments.
Examples of plants or apparatuses where the present invention can be applied are steelmaking electric furnaces, gas heating furnaces, coke ovens, glass melting furnaces, hot gas stacks, nuclear plants, buildings or rooms on fire, reheating furnaces, confined areas with possibly toxic conditions, etc. These plants or apparatuses require periodical visual inspections of their conditions (for example, where they are coated with refractory material, in order to determine the degree of wear of the coating due to their normal functioning) and, if necessary, effect the necessary repairs for avoiding costly damage or an extensive and unexpected shut-down periods with the consequent production losses.
It is known in the state of the art that, even with a protection system (for example, cooling systems used for protecting cameras from high temperatures), the survival time of a camera in a hostile environment, i.e. with temperature characteristics and/or atmospheric contaminants harmful or dangerous for human beings, for example in a steel production furnace, is limited, and there is therefore the necessity of a control system that can produce a detailed view of the environment in an extremely short time, but with specific details and a visual amplitude that are such as to allow the operator and/or maintenance personnel to take decisions which may cause stoppage for effecting repairs or maintenance on the equipment monitored or continuation of the production.
It is also known also that display systems having a camera mounted on a movable base so that it can be moved by remote control in different directions—for example by means of a robot or a PTZ (pan-tilt-zoom) system—are not practical as the time for the inspections is sometimes extremely short and the limited field of view of this device imposes a constraint in the already limited time for the inspection, as the operator must manually direct the camera to look for faults, and also because the moving parts and mechanical/electrical components of the camera system tend to deteriorate as a result of the high temperatures, dusty environments or more generally due to the aggressive conditions of such environments.
The known practice also provides for undertaking rapid inspections, using conventional cameras, both fixed and movable, used during non-operational intervals or through small peep windows with a limited viewing angle and short-term assessments (in the necessity of continuing the production cycles of the equipment) or using a camera that can be moved in different directions to be focused on the desired areas on the inner side of the equipment, but always for short periods of time.
As can be easily understood from the above description, the known solutions have significant limitations and are not entirely satisfactory.
More specifically, the current praxis and technology used for inspecting and monitoring equipment, for example high-temperature furnaces, such as electric arc furnaces for the production of steel, have certain limitations; in order to effect an accurate control of the inside of the electric furnace for example, the cameras should remain inside the furnace for a longer period of time than the time currently allowed in a normal shutdown, i.e. during the time following each casting, after the discharging of the liquid steel and beginning of the loading of the subsequent ferrous materials.
Even if the camera used for the control is equipped with a good cooling system, it can hardly resist the temperature of the furnace, which can exceed 1,000° C. in some cases.
Under these conditions, the camera can remain in this environment for much less than a minute, with a consequent limitation in the data that can be collected.
The remaining mechanical/electrical/electronic movable devices necessary for the functioning of the camera (focusing, movement, etc.) also have a short lifespan within these hot environments.
Various proposals have been found in the prior art aimed at solving the problem of the inspection of industrial plants, using video-cameras.
U.S. Pat. No. 5,162,906 of Yorita el al. describes an apparatus for observing the interior of a hot furnace using a camera protected by a water-cooled casing and also being cooled by blowing cooling air in order to keep the camera at a temperature of 50° C. or less, whereas the temperature of the furnace is about 1,200° C. The apparatus of Yorita can be used for the inspection of the refractory coating of coke ovens, blast-furnaces, metal mixers, mixing containers, etc. This solution, however, does not allow a complete image of the interior of the furnace to be revealed, or alternatively it requires relatively lengthy times, incompatible with the exposure time of the video camera to heat; the analysis, moreover, can only be effected in conjunction with the data recovery.
U.S. Pat. No. 6,111,599 in the name of Nance, is also aimed at protecting the camera from hostile environmental conditions, wherein the camera is inserted within a transparent double-wall group. This solution on the whole has limits analogous to those indicated above.
U.S. Pat. No. 6,229,563 in the name of Miller II et al. discloses a monitoring system for a furnace wherein the temperature often exceeds 2,000° F. A camera mounted at the end of a fluid-cooled lance is introduced into a furnace by an operator outside the furnace. A video-camera is used for inspecting a high-temperature furnace: the video-camera allows any part of the furnace to be accurately viewed.
Although this solution is functional, it requires a relatively lengthy time for directing the video-camera in the various sensitive areas of the furnace in order to frame them.
The document WO 2014/152855 A2 describes a camera-mounting system, having a plurality of cameras, wherein the lens of each camera is oriented towards an area of interest, so that they can provide a completely spherical obstruction-free image or video. Although in some ways interesting, the embodiment described in this patent, however, cannot be used for controlling hostile environmental spaces or for recording the images of an industrial plant for detecting wear variations that require preventive or corrective actions for maintaining the production capacity of these plants; the data that can be obtained, moreover, are purely image data.
US patent application No. 2015/0285559 describes a device for monitoring inside a high-temperature furnace, comprising one or two cameras that are introduced into the high-temperature furnace and used for determining the size of the deposits in a melting furnace. This solution, however, uses stereography for generating a 3D estimation of a limited area, thus having a relatively restricted breadth of vision of the furnace, in addition to substantially having the same drawbacks as the first two documents mentioned.
The documents cited in this text (comprising the patents previously listed), and all the documents mentioned or indicated in the documents cited in this text, are incorporated herein for reference. Documents incorporated for reference in the present text or any teaching therein, can be used in the practice of the present invention.
U.S. Pat. No. 3,504,122 relates to a stereoscopic television system with means for controlling the movement of the video-camera from a remote location.
U.S. Pat. No. 4,131,914 relates to a method and apparatus for inspecting the refractory coating in a furnace. This system is composed of a video-camera mounted in a cooled container, which, by means of a cable, transmits a television signal outside the furnace, which is then displayed in real time in an external monitor.